diff options
Diffstat (limited to '')
| -rw-r--r-- | src/backend/executor/nodeModifyTable.c | 46 |
1 files changed, 38 insertions, 8 deletions
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c index 6fea82e..1ad5dcb 100644 --- a/src/backend/executor/nodeModifyTable.c +++ b/src/backend/executor/nodeModifyTable.c @@ -2947,8 +2947,29 @@ lmerge_matched:; case TM_SelfModified: /* - * The SQL standard disallows this for MERGE. + * The target tuple was already updated or deleted by the + * current command, or by a later command in the current + * transaction. The former case is explicitly disallowed by + * the SQL standard for MERGE, which insists that the MERGE + * join condition should not join a target row to more than + * one source row. + * + * The latter case arises if the tuple is modified by a + * command in a BEFORE trigger, or perhaps by a command in a + * volatile function used in the query. In such situations we + * should not ignore the MERGE action, but it is equally + * unsafe to proceed. We don't want to discard the original + * MERGE action while keeping the triggered actions based on + * it; and it would be no better to allow the original MERGE + * action while discarding the updates that it triggered. So + * throwing an error is the only safe course. */ + if (context->tmfd.cmax != estate->es_output_cid) + ereport(ERROR, + (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION), + errmsg("tuple to be updated or deleted was already modified by an operation triggered by the current command"), + errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows."))); + if (TransactionIdIsCurrentTransactionId(context->tmfd.xmax)) ereport(ERROR, (errcode(ERRCODE_CARDINALITY_VIOLATION), @@ -2956,6 +2977,7 @@ lmerge_matched:; errmsg("%s command cannot affect row a second time", "MERGE"), errhint("Ensure that not more than one source row matches any one target row."))); + /* This shouldn't happen */ elog(ERROR, "attempted to update or delete invisible tuple"); break; @@ -3064,19 +3086,27 @@ lmerge_matched:; /* * This can be reached when following an update * chain from a tuple updated by another session, - * reaching a tuple that was already updated in - * this transaction. If previously modified by - * this command, ignore the redundant update, - * otherwise error out. - * - * See also response to TM_SelfModified in - * ExecUpdate(). + * reaching a tuple that was already updated or + * deleted by the current command, or by a later + * command in the current transaction. As above, + * this should always be treated as an error. */ if (context->tmfd.cmax != estate->es_output_cid) ereport(ERROR, (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION), errmsg("tuple to be updated or deleted was already modified by an operation triggered by the current command"), errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows."))); + + if (TransactionIdIsCurrentTransactionId(context->tmfd.xmax)) + ereport(ERROR, + (errcode(ERRCODE_CARDINALITY_VIOLATION), + /* translator: %s is a SQL command name */ + errmsg("%s command cannot affect row a second time", + "MERGE"), + errhint("Ensure that not more than one source row matches any one target row."))); + + /* This shouldn't happen */ + elog(ERROR, "attempted to update or delete invisible tuple"); return false; default: |